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That's a great article
McGuire Ballistics Field Reports
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DRock
Well-Known Member
Can I ask a question about neck tension? I am worried that .001 isnt enough neck tension to prevent the projectile from dislodging in the magazine with recoil? I have always heard minimum of .003 neck tension for hunting ammunition. I see a ton of kills so I know you are not using your reloads just on targets-- is .0005 and .001 neck tension enough to secure the bullet without fear of it moving with recoil or a bumping around on a dirt road for miles?? I am headed moose and grizzly hunting soon and dont want to have any issues with my ammo--that little neck tension concerns me with a hunting load?
Rifleman97
Well-Known Member
Neck tension in terms of just interference diameters alone means very little. What is your bullet diameter, neck length, and neck wall thickness? For example my 257 weatherby I'm getting .001 neck tension and it seems to hold perfectly well under recoil, however there's 2 things that greatly help this. One, is that 257 weatherby has a very long neck, and Peterson brass has a bit thicker neck than norma brass from my measurements. Secondly, I'm seating the bullets such that my case mouth is at the back of one of the grooves. Because of this, a very slight crimp puts pressure against the back of the bullet, which means under recoil the case mouth prevents the bullet from being able to move back without significant pressure.
DRock
Well-Known Member
I appreciate your response very much. I am shooting a custom built 300PRC 8 twist with Lapua brass and trying to get the 195 Copper Rose magazine feed bullet to shoot. I feel like I am the only one on the forum that hasn't had an easy experience getting good groups with my copper rose bullets. I have been setting neck tension to .003 (because that was what my previous research told me I should do for a hunting round). I read on here that Sam was recommending .001 or even .0005 neck tension and was getting best accuracy this way. Concerned that for a hunting scenario--especially where dangerous game could come in play-- that there is potential for the bullets to move out of the case mouth with the heavy recoil of the PRC.
I just ordered the .307 expander mandrel on the McGuire website to see if reducing neck tension will improve my groups but just wanted to make sure I wasn't opening myself up for potential issues with my ammo.....
I just ordered the .307 expander mandrel on the McGuire website to see if reducing neck tension will improve my groups but just wanted to make sure I wasn't opening myself up for potential issues with my ammo.....
Rifleman97
Well-Known Member
I've noticed with them that group size changes a lot more with slight powder charge changes than seating depth. Changing powders likely also has an effect so it might just not like the pressure curve of the powder you're using. Try minimal neck tension with a seating depth of the case mouth against the back of one of the bands with a slight crimp. The crimp won't change your bullet grip since it will be crimping into the space between grooves, but is to prevent the bullet getting Pushed back under recoil as 300prc has a decent bit. Lapua 300prc brass has a pretty thick neck and 300prc has a long enough neck, so you should be all good there. And remember that there's spring back so your .001 mandrel is more like .0015-.002 actual interference. I've talked to Sam and he's had good luck with larger than bullet diameter sized mandrels, since with spring back it still has enough to hold it. However I definitely wouldn't go that far for a magazine fed rifle, only single feeding.
Wishing you luck getting them to shoot! If you post here what you've tried and the groups you've got some others may be able to chime in as well with some ideas as well.
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I have not had any issues with bullets moving using .0005-.001 but have seen creating a compression blow out when using too much neck tension. If you are getting bullets moving from recoil the tip will collapse before that happens generally. When you are expanding necks, you are not directly taking neck to that size due to spring back. Virgin brass seems to really need the .0005 under especially when they come in way under bullet diameter. As you resize you can move to a smaller diameter as you see fit.
DRock
Well-Known Member
Thank you for explaining this to me... the spring back makes total sense. I ordered the .307 expander mandrel and look forward to seeing how changing the neck tension can help with accuracy. Thank you very much for taking time to respond! Hopefully I will have moose and grizzly photos to add to this thread in the near future!
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Thank you sir!!! The .001 works great as well. If its fighting you dont be afraid to hit them again.
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DRock
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LOL--definitely wont let my pride limit me to a one shot kill!! Thanks again!
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Powder is a major factor. Don't get attached to a powder. My rule is start at a safe charge and go up .5GR until it shoots. If it doesn't aquire precision before you reach preasure or case fill change powder accordingly. Finding a powder that gives a wide precision mark on multiple grains of powder is optimal. Recheck gun cold and at distance to make sure load is stable in a cold gun. I had this with a 7PRC recently. I have had great luck with retumbo so that is where I started. The new 151 OSN proto showed no sighns through loading and with very little data on bullet had me questioning if there was a problem with bullet. I forced myself to go with N560 and it had a 2GR mark where it shot same point of impact and all 12 rounds would have basically fit into a .5MOA. The powder is where I would look to first. 300PRC I would try that with n560, H4831sc, N565, Retumbo to start with a .001-.0005 mandrel and see how that goes. The one place I have seen to be a major problem with our bullets is if a barrel is oversized. I have seen a few of them now and they can be very frustrating. Copper solids seem to be affected more by this than a lead cup and core. During development you will see 15-25fps increase per .5GR and closer you get to preasure that will increase. Around 1-2GR below first felt preasure you that will increase by 50+ fps and I usually find my best load in this window. On a loose barrel you will not see this preasure window. It will just increase 15-25fps through development until it hits preasure and there will be no ryme or reason to group size. Let me know if this helps and if I can help in any way.
Below is the first spot the 7prc shot and 1.5-2GR later.
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So the C&C bullets swell enough to "fit" the oversized bore/grooves?Powder is a major factor. Don't get attached to a powder. My rule is start at a safe charge and go up .5GR until it shoots. If it doesn't aquire precision before you reach preasure or case fill change powder accordingly. Finding a powder that gives a wide precision mark on multiple grains of powder is optimal. Recheck gun cold and at distance to make sure load is stable in a cold gun. I had this with a 7PRC recently. I have had great luck with retumbo so that is where I started. The new 151 OSN proto showed no sighns through loading and with very little data on bullet had me questioning if there was a problem with bullet. I forced myself to go with N560 and it had a 2GR mark where it shot same point of impact and all 12 rounds would have basically fit into a .5MOA. The powder is where I would look to first. 300PRC I would try that with n560, H4831sc, N565, Retumbo to start with a .001-.0005 mandrel and see how that goes. The one place I have seen to be a major problem with our bullets is if a barrel is oversized. I have seen a few of them now and they can be very frustrating. Copper solids seem to be affected more by this than a lead cut and core. During development you will see 15-25fps increase per .5GR and closer you get to preasure that will increase. Around 1-2GR below first felt preasure you that will increase by 50+ fps and I usually find my best load in this window. On a loose barrel you will not see this preasure window. It will just increase 15-25fps through development until it hits preasure and there will be no ryme or reason to group size. Let me know if this helps and if I can help in any way.
Below is the first spot the 7prc shot and 1.5-2GR later.
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Definitely seems to be less susceptible...
DRock
Well-Known Member
This is really helpful-- I appreciate very much you taking time to walk me through this process. Hopefully I dont have a loose barrel but I have wondered if my issues are gun related since the majority of people on this thread are finding load development to be very simple. I will try some different powders this weekend and hopefully I will find the sweet spot and get things dialed in so I can start shooting at distance. Invaluable advice. I have been very intrigued by reading the comments and seeing all the photos on this thread but even more impressed with the generous help from you and other members to help me figure out load development. Thank you sincerely!Powder is a major factor. Don't get attached to a powder. My rule is start at a safe charge and go up .5GR until it shoots. If it doesn't aquire precision before you reach preasure or case fill change powder accordingly. Finding a powder that gives a wide precision mark on multiple grains of powder is optimal. Recheck gun cold and at distance to make sure load is stable in a cold gun. I had this with a 7PRC recently. I have had great luck with retumbo so that is where I started. The new 151 OSN proto showed no sighns through loading and with very little data on bullet had me questioning if there was a problem with bullet. I forced myself to go with N560 and it had a 2GR mark where it shot same point of impact and all 12 rounds would have basically fit into a .5MOA. The powder is where I would look to first. 300PRC I would try that with n560, H4831sc, N565, Retumbo to start with a .001-.0005 mandrel and see how that goes. The one place I have seen to be a major problem with our bullets is if a barrel is oversized. I have seen a few of them now and they can be very frustrating. Copper solids seem to be affected more by this than a lead cut and core. During development you will see 15-25fps increase per .5GR and closer you get to preasure that will increase. Around 1-2GR below first felt preasure you that will increase by 50+ fps and I usually find my best load in this window. On a loose barrel you will not see this preasure window. It will just increase 15-25fps through development until it hits preasure and there will be no ryme or reason to group size. Let me know if this helps and if I can help in any way.
Below is the first spot the 7prc shot and 1.5-2GR later.
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The barrel issue is very very rare so I definitely would not worry about it. Yeah allot or helpful folks on here. My way is not the only way and I am always willing to add to my process but that is the process that works for me. Lets get ya rolling!!!
